OTTAWA - A Conservative claim that New Democrats have a carbon-tax policy has been roundly denounced as hypocritical at best and untrue at worst — but don't expect the campaign to end anytime soon.

It's called framing the issue, in political parlance, and the continuing barrage by the Harper Conservatives to tag the NDP with a carbon-tax policy it does not endorse, is a case study.

NDP Leader Tom Mulcair appealed to journalists this week to debunk the Conservative spin, which has been airing since at least May and hit a crescendo this week with the return of Parliament for the fall sitting.

A volley of media fact-checking had already showed that the alleged "job killing carbon tax" was effectively the same cap-and-trade policy the Conservatives themselves championed in their 2008 election platform — while running against a true carbon-tax policy proposed by the Liberals.

Undeterred, the Conservatives are maintaining course in the House of Commons, continuing a campaign that's included carbon-tax TV ads, letters to the editor, caucus talking points and scripted MP statements before the daily question period.

"If the NDP is going to attempt to challenge the government on its (sound) handling of the economy, they should expect to not only hear about our government's strong record of job creation, strong support for lower taxes, and unyielding efforts to open up new markets for Canadian businesses," Andrew MacDougall, Prime Minister Stephen Harper's communications director, said in an email exchange with The Canadian Press.

"They should also expect to hear why their plans to raise taxes, call entire sectors of the economy a 'disease,' and oppose new trade deals are bad for the economy."

But what about that 2008 Conservative campaign promise of a cap-and-trade system, similar to the NDP's?

"That's the past," responded MacDougall. "Our 2011 platform stands. So does the NDP's — and that includes their plan to 'put a price on carbon.'"

The truthiness of the carbon-tax claim is almost beside the point.

Conservative Agriculture Minister Gerry Ritz actually winked across the aisle Wednesday at New Democrats after reading his "job-killing carbon tax" talking point from a sheet of paper.

"People are getting lost — and the Conservatives won't mind this — in the 'Mulcair supports the carbon tax' or 'no he doesn't' debate," Tim Powers, an Ottawa lobbyist and well-connected Conservative strategist, said in an interview.

"As long as a conversation continues about what Mulcair does and doesn't support, he's in a defensive position."

That, in essence, is "agenda-setting at its finest."

"It's not about necessarily winning converts from the other side," said Powers.

"It's about raising questions and creating uncertainty that could lead to moving a small mass of people to your side."

The tactic is becoming an issue for journalists in what is being called the "post-truth" era of political messaging, especially during a heated U.S. presidential race.

Major publications such as the New York Times and the Atlantic Monthly are having anguished discussions, played out on their editorial pages, over how to report fairly and accurately in the face of relentless distortion campaigns that don't pause when fact-checked.

"The media thinks that once they've said it once, they're bored with it," said pollster Allan Gregg, the chairman of Harris-Decima who once advised Conservative prime minister Brian Mulroney.

"So if you're only relying on an earned media strategy to rebut this stuff, you're going to lose."

Elly Alboim, a principal with the Earnscliffe Strategy Group in Ottawa who specializes in strategic communications, said such campaigns "are very hard to counter."

"If you're willing to say things that distort reality in a significant way, if you want to make claims that have a kernel of truth but are generally wrong, and you're willing to disseminate them widely, you've got a tremendous advantage," said the former Parliament Hill bureau chief for the CBC.

Alboim said the Conservatives understand that alienation from politicians and the political process means the vast majority of Canadian voters don't consume political news.

"To penetrate the public consciousness is very, very difficult. So the awareness of the counter argument (on the carbon-tax claim) will be very low."

That's one factor working in the Tories' favour: a deep-pocketed and disciplined message machine with the means and the will to keep repeating their line.

There may be another.

Powers noted that highly controversial claims only work if the party proposing them has public credibility. He said the well-documented public belief in the Harper Conservatives' economic credentials could help give their argument weight.

He contrasted the situation to a Liberal claim from the 2006 election campaign, in which Harper was accused of plotting to create a kind of military state.

"When the 'soldiers in the streets with guns' came out, it came out at a time when the Liberal party's credibility was eroding," said Powers.

Media and public reaction was withering.

The difference in this new "post-truth" political atmosphere is that the Liberal slur — briefly floated as an Internet trial balloon that never actually aired on TV — was immediately disowned by the party and never repeated.

Today, political parties double down on their whoppers in recognition that if you repeat them often enough, someone will believe them.

And negative media coverage simply fans the flames.

"I think there's an acknowledgment that hasn't been there before that political parties look at media outlets as participants — as opposed to neutral observers — in the drama," said Powers.

In as much as news media continue to write about the contretemps, said Powers, "you are part and parcel of the story."

"Where do you draw the line between covering a story, then becoming an aggregator of a deliberate political strategy?"